1. Field of the invention
The present invention relates to a method and a system for observing a biological sample.
2. Description of Related Art
Continuous observation of the change in growth over time of the bacterium is useful in medicine bacterium is very convenient from various viewpoints of medicine, pharmacology, agriculture and biology; because continuous observation makes it possible to obtain more information than that obtained in interval observation. In order to continuously observe the change over time of the biological samples, while maintaining a contact temperature, moisture and concentration of carbon dioxide in the sample, it has been necessary to assemble a recording means such as a video camera on a biological microscope and to install a thermostat, a hygrostat and a carbon dioxide gas supplying device on a sample stage of the microscope. This biological sample observation system has been disadvantageous in that various conditions such as the temperature can vary, and therefore, it is difficult to create on the sample stage the same condition as that realized in an incubator.
In order to overcome the above mentioned disadvantage, the applicant proposed a biological sample observation system using a solid state image sensor, in Japanese Patent Application No. 106471/1991 filed on Apr. 4, 1991, which was laid open on Nov. 6, 1992 under Japanese Patent Laid-open Publication No. Hei 4-316478, and which has a corresponding EPC application No. 92 303 257 laid open under Publication EP-A2-508828 on Oct. 14, 1992 and a corresponding U.S. patent application Ser. No. 07/866,008, contents of which are incorporated herein by this reference.
In the proposed biological sample observation system, a sample, holder has a solid state image sensor accommodated in the bottom recessed portion of the sample holder, and the sample is located in and supported by the sample holder in such a manner that the portion of the sample to be observed is positioned just above a photoreception face of the solid state image sensor with no magnifying optical lens interposed between the sample and the solid state image sensor. A filter and a light source are located above the sample, so that light emitted from the light source is irradiated through the filter and then to the sample and then to the photoreception face of the solid state image sensor. The solid state image sensor is driven by a drive unit, and image information is transferred from the solid state image sensor through the driving circuit to a record and display unit, so that an observed sample image is displayed and recorded.
In the above mentioned biological sample observation system, the part excluding the drive unit and the record and display unit is very small in size and can sustain a high temperature and a high moisture. Therefore, the part excluding the drive unit and the record and display unit can be located within an incubator which allows the temperature, the moisture and the concentration of gas such as carbon dioxide to be maintained at a constant. Accordingly, it is possible to make a continuous observation of change with time of a biological sample under a preferred temperature, moisture and concentration of gas.
In the above mentioned biological sample observation system, however, the solid state image sensor and the light source have been continuously and ceaselessly energized during a period in which the sample is being observed. Therefore, if the observation is continued for a long period of time in this biological sample observation system, the heat emitted from the solid state image sensor and the light source will gradually elevate the temperature of the sample. The temperature elevation of the sample gives an adverse affect to the growth of sample cells or to the reproduction of sample fungi or sample bacterium. Therefore, in the above mentioned biological sample observation system, it has been difficult to continuously observe the sample for a long period of time as it is with no adverse influence to the biological sample.